CN114377559A - Super-hydrophobic nano-cellulose moisture-resistant air purification membrane and preparation method thereof - Google Patents

Abstract

The invention discloses a super-hydrophobic nano-cellulose humidity-resistant air purification membrane and a preparation method thereof, and the nano-cellulose air purification membrane with super-hydrophobic property is obtained, so that the nano-cellulose air purification membrane can be stably filtered under the high-humidity environment condition. The invention adopts a form of combining green chemical modification and freeze drying process, and the method has the advantages of safety, stability, simple production process and low process cost.

Description

Superhydrophobic nanocellulose anti-moisture air purification membrane and preparation method thereof

【Technical field】

The invention relates to the technical field of air purification membranes, in particular to a superhydrophobic nanocellulose anti-moisture air purification membrane and a preparation method thereof.

【Background technique】

Sustainable development is the basic concept of current social development, and it is imperative to replace non-renewable materials with plant-derived materials. Since the new coronavirus hit the world, the manufacture of air filtration equipment has risen rapidly, among which mask filter elements are the main representatives. Relevant data shows that the production capacity of mask filter elements has nearly tripled in 2020. At this stage, the filter element of the mask still uses petroleum derivative polypropylene as the main material source. The increase in production capacity will inevitably increase carbon emissions. At the same time, the defect that cannot be naturally degraded will cause secondary pollution to the ecological environment.

Based on this, the preparation of high-efficiency air purification membranes based on degradable nanocellulose from plant fibers has become a research hotspot at this stage. There are related studies, such as Chinese Patent Application No. 201810717317.5 A cellulose-polyamide anti- Electrostatic air purification composite membrane and preparation method. In the method, graphene oxide and tetracarboxylated iron phthalocyanine are added to the spinning emulsion of cellulose/polyamide, and the emulsion is broken during solidification, so that graphene oxide is precipitated and deposited on the composite nanomembrane. The surface of the composite film is further grafted with a layer of iron tetracarboxyphthalocyanine. The prepared composite film can make full use of the catalytic oxidation ability of iron tetracarboxyphthalocyanine to formaldehyde, the efficient and permanent removal of formaldehyde, and the elimination of static electricity in time. Prevent dust adsorption, prevent membrane hole clogging, good durability, long service life, can be widely used in the field of air purification. Another example is Chinese Patent Application No. 201710587286.1 A preparation method of negative ion air purification membrane, with cellulose acetate as the main material, being dissolved in a single solvent or mixed solvent, and the obtained mixed fiber solution is mixed with the modified ice stone powder again. A new type of negative ion air purification membrane was prepared by electrospinning. The surface density of the prepared membrane was 30-120g/m ² , the thickness was 0.3-0.8mm, and the tensile strength was 8-15KN/M. The air purification membrane is prepared by using cellulose acetate as the main component. The method is simple. Add the ice stone powder to the purification membrane, and at the same time filter the air, it also brings negative ions to achieve the purpose of purifying the air.

However, plant fiber nanocellulose is a kind of hydrophilic fiber, and the basic characteristics of the material limit its application in different scenarios, especially in the environment of high humidity and high temperature difference, which is manifested in the following two points: 1. Plant fibers are easy to absorb moisture and swell in a humidity environment, resulting in softening of the fiber structure, and finally the fiber network structure collapses under the pressure difference environment during use, losing the most basic filtration performance; 2. The electrospinning membrane of the electrostatic cylinder is subject to high The interference of water molecules in the humid air causes the loss of the surface charge carried by it, which reduces the filtration efficiency dominated by electrostatic adsorption. In practical environmental conditions, the relative humidity (RH) of the air in tropical or subtropical regions can be as high as 80-90%, and breathing through the mouth and nose of the human body will generate aerosol moist hot air containing about 85-95% RH. When there is a certain temperature difference between the two ends of the air purification membrane, based on the condensation effect, the moisture flow will be condensed to form droplets when passing through the filter medium. This condensation phenomenon is devastating to the structure of fiber filtration membranes. On the one hand, hydrophilic fibers absorb droplets, resulting in a sharp drop in mechanical properties, and the membrane has insufficient tensile and bending resistance; on the other hand, capillary force causes The trapped droplets condense between the fibers to form a liquid film, which reduces the airflow path of the filter medium and increases the filtration resistance.

Therefore, the lack of moisture resistance of nanocellulose air purification membranes at this stage is a key factor limiting its application.

[Content of the invention]

Aiming at the problem of insufficient moisture resistance of nanocellulose air purification membranes in the prior art, the present invention provides a superhydrophobic nanocellulose antihumidity air purification membrane and a preparation method thereof, and obtains a nanocellulose air purification with superhydrophobic properties Membrane, to achieve stable filtration of nanocellulose air purification membrane under high humidity environmental conditions. The invention adopts the form of combining green chemical modification and freeze-drying process, and the method has the advantages of safety and stability, simple production process and low process cost.

The object of the present invention is achieved through the following technical solutions:

The preparation method of the super-hydrophobic nanocellulose anti-moisture air purification membrane comprises the following steps:

1) Prepare 40-60 parts by weight of nanocellulose, 0.1-1 part of methyltrimethoxysilane, 40-60 parts of tert-butanol, 2-4 parts of purified water, and mix the nanocellulose and tert-butanol evenly , and placed under ultrasonic conditions to homogenize;

2) Adjust pH=4 with pure water, add methyltrimethoxysilane, and stir to prepare a silane hydrolyzed solution;

3) Mix the material obtained in step 2) with the material obtained in step 1), carry out a modification reaction under stirring conditions, use a custom mold to shape after the modification reaction, freeze-dry, and anneal at high temperature to obtain superhydrophobic nanofibers Anti-moisture air purification membrane.

In the present invention:

In step 1), according to the weight ratios of 50 parts of nanocellulose, 0.5 parts of methyltrimethoxysilane, 50 parts of tert-butanol, and 3 parts of pure water; the described stirring is uniform, using magnetic stirring for 30min; the ultrasonic conditions, its power is 100W, and the time is 10min.

In step 2), the stirring is uniform, using magnetic stirring for 10 min.

In step 3), the modification reaction is carried out under stirring conditions, and the modification is carried out under magnetic stirring for 2 h; the modification is carried out using a custom mold, wherein the size of the mold is R=6cm, and the height is 2cm; the Freeze drying is first placed in a refrigerator, pre-frozen at -20°C for 6 hours, and then placed at -56°C for drying for 48 hours; the high-temperature annealing is performed at a temperature of 80°C for 2 hours.

The effect of each component in the present invention is as follows:

Nanocellulose: the supporting skeleton of the air purification membrane, the basic source of the filtration effect.

Methyltrimethoxysilane: Nanocellulose hydrophobic modifier, used to achieve superhydrophobic properties of nanocellulose.

Tert-Butanol: Makes nanocellulose form uniform and fine pores during the freeze-drying process, improving filtration performance.

Hydrochloric acid: Conditional methyltrimethoxysilane hydrolyzes the pH value of the environment, so that silane is hydrolyzed stably.

The invention also relates to a super-hydrophobic nano-cellulose anti-moisture air purification film obtained by using the above-mentioned preparation method of the super-hydrophobic nano-cellulose anti-moisture air purification film, the density is 0.0119-0.0153g/cm ² , the porosity reaches 99.0-99.2%, The water contact repose angle reaches 138.5°-154.2°, the water contact rolling angle is 5.3°-7.2°, the filtration efficiency for PM2.5 reaches 99.24-99.73%, and the filtration resistance is lower than 100Pa (51-82Pa), and the quality factor reaches 0.076-0.122Pa ^-1 , which meets the needs of commercial air filter materials.

Compared with the prior art, the present invention has the following advantages:

1. The preparation method of the super-hydrophobic nanocellulose anti-moisture air purification film of the present invention adopts the chemical modification method to modify the nanocellulose, and the modification of methyltrimethoxysilane enhances the nanocellulose. The hydrophobic performance achieves the super-hydrophobic effect (the repose angle of water contact is 138.5°-154.2°, and the rolling angle of water contact is 5.3°-7.2°), which is beneficial to the anti-interference ability of nanocellulose air purification membrane to moisture in the air, In addition, the method has the advantages of simple and effective process, no toxicity, no risk of environmental pollution, low production energy consumption, easy to realize industrialization, and further enhances the potential of industrial application of nanocellulose.

2. The super-hydrophobic nanocellulose anti-moisture air purification membrane obtained by the present invention can significantly improve the anti-moisture filtration performance of the nanocellulose air purification membrane, and ensure its high-efficiency particulate filtering efficiency, reduce particulate filtering resistance, and be compatible with existing Compared with other products, the anti-humidity performance is improved by about 50 times, and the increase rate of anti-humidity filtration resistance is less than 15%. At the same time, the addition of tert-butanol preserves the highly uniform and dense pore structure of nanocellulose, with a density of 0.0119-0.0153g/cm ² and a porosity of 99.0-99.2%, realizing the high-efficiency filtration performance of the nanofiber air purification membrane. The filtration efficiency of PM2.5 reaches 99.24-99.73%, the filtration resistance is lower than 100Pa, and the quality factor reaches 0.076-0.122Pa ^-1 , which meets the needs of commercial air filter materials.

【Description of drawings】

Fig. 1 is the process flow diagram of the preparation method of the superhydrophobic nanocellulose anti-moisture air purification membrane of the present invention.

【Detailed ways】

The specific embodiments of the present invention will be further described below with reference to the examples.

Example 1:

The preparation method of the super-hydrophobic nanocellulose anti-moisture air purification membrane comprises the following steps:

1) Prepare 50g of nanocellulose, 0.5g of methyltrimethoxysilane, 50g of tert-butanol, 3g of purified water, and mix the nanocellulose and tert-butanol by magnetic stirring for 30min, and place them under ultrasonic conditions to homogenize ( Power: 100W, time 10min);

2) Adjust pH=4 with pure water, add methyltrimethoxysilane, stir evenly (magnetic stirring for 10min) to prepare a silane hydrolyzate;

3) Mix the material obtained in step 2) with the material obtained in step 1), carry out the modification reaction under magnetic stirring for 2h, and use a custom mold (the size of the mold R=6cm, the height is 2cm) to shape after the modification reaction is finished. , freeze-drying (pre-freeze at -20°C for 6h, and then place at -56°C for drying for 48h), high temperature annealing (annealing temperature 80°C, time 2h) to obtain superhydrophobic nanocellulose anti-moisture air purification membrane;

The obtained superhydrophobic nanocellulose anti-moisture air purification membrane has a density of 0.0123 g/cm ² , a porosity of 99.1%, a water contact repose angle of 147.8°, a water contact rolling angle of 6.4°, and the filtration efficiency of PM2.5 It reaches 99.56%, the filtration resistance is 51Pa, and the quality factor reaches 0.107Pa ^-1 .

Example 2:

The preparation method of the super-hydrophobic nanocellulose anti-moisture air purification membrane comprises the following steps:

1) Prepare 40g of nanocellulose, 1g of methyltrimethoxysilane, 40g of tert-butanol, 4g of purified water, mix the nanocellulose and tert-butanol by magnetic stirring for 30min, and place them under ultrasonic conditions to homogenize (power : 100W, time 10min);

2) Adjust pH=4 with pure water, add methyltrimethoxysilane, stir evenly (magnetic stirring for 10min) to prepare a silane hydrolyzate;

3) Mix the material obtained in step 2) with the material obtained in step 1), carry out the modification reaction under magnetic stirring for 2h, and use a custom mold (the size of the mold R=6cm, the height is 2cm) to shape after the modification reaction is finished. , freeze-drying (pre-freeze at -20°C for 6h, and then place at -56°C for drying for 48h), high temperature annealing (annealing temperature 80°C, time 2h) to obtain superhydrophobic nanocellulose anti-moisture air purification membrane;

The obtained superhydrophobic nanocellulose anti-humidity air purification membrane has a density of 0.0151 g/cm ² , a porosity of 99.0%, a water contact repose angle of 154.2°, a water contact rolling angle of 5.3°, and the filtration efficiency of PM2.5 It reaches 99.73%, the filtration resistance is 82Pa, and the quality factor reaches 0.076Pa ^-1 .

Example 3:

The preparation method of the super-hydrophobic nanocellulose anti-moisture air purification membrane comprises the following steps:

1) Prepare nanocellulose 60g, methyltrimethoxysilane 0.1g, tert-butanol 60g, purified water 2g, mix nanocellulose and tert-butanol by magnetic stirring for 30min, and place them under ultrasonic conditions to homogenize ( Power: 100W, time 10min);

2) Adjust pH=4 with pure water, add methyltrimethoxysilane, stir evenly (magnetic stirring for 10min) to prepare a silane hydrolyzate;

3) Mix the material obtained in step 2) with the material obtained in step 1), carry out the modification reaction under magnetic stirring for 2h, and use a custom mold (the size of the mold R=6cm, the height is 2cm) to shape after the modification reaction is finished. , freeze-drying (pre-freeze at -20°C for 6h, and then place at -56°C for drying for 48h), high temperature annealing (annealing temperature 80°C, time 2h) to obtain superhydrophobic nanocellulose anti-moisture air purification membrane;

The obtained superhydrophobic nanocellulose anti-moisture air purification membrane has a density of 0.0119 g/cm ² , a porosity of 99.2%, a water contact repose angle of 138.5°, a water contact rolling angle of 7.2°, and the filtration efficiency of PM2.5 It reaches 99.24%, the filtration resistance is 52Pa, and the quality factor reaches 0.122Pa ^-1 .

Example; Process Screening:

Table 1 Material ingredient list

The different process technology options are as follows:

(1) Take 40% nanocellulose and put it in a beaker, add 40% tert-butanol under the action of magnetic stirring, stir for 30 minutes to make it evenly mixed, and then homogenize it by ultrasonic (power: 30%, time 10 minutes). quality treatment. To prepare methyltrimethoxysilane separately, first take an appropriate amount of deionized water in a beaker, adjust the pH of the aqueous solution to 4 with hydrochloric acid, and then dropwise add 1% methyltrimethoxysilane to hydrolyze under the action of magnetic stirring for 10 minutes to obtain methyltrimethoxysilane. The hydrolyzed solution of trimethoxysilane was reserved for future use. An appropriate amount of methyltrimethoxysilane hydrolyzate was added to the nanocellulose/tert-butanol mixed solution, modified under the action of magnetic stirring for 2 hours, and poured into a customized mold (R=6cm) after the modification was completed. Then it was placed in a refrigerator (-20°C) for 6 hours, and then freeze-dried (-56°C, 48h). The freeze-dried samples were taken out and sealed, and annealed in a high-temperature oven at 80°C for 2 hours to obtain the final result. sample.

(2) The difference from (1) lies in the ratio of ingredients, and the corresponding ingredients are: 40% nanocellulose, 50% tert-butanol.

(3) The difference from (1) lies in the ratio of ingredients, and the corresponding ingredients are: 40% nanocellulose, 59% tert-butanol.

The difference between (4) and (1) is that the ratio of ingredients is different, and the corresponding ingredients are: 50% nanocellulose, 40% tert-butanol.

The difference between (5) and (1) is that the proportion of ingredients is different, and the corresponding ingredients are: 50% nanocellulose, 50% tert-butanol.

(6) The difference from (1) lies in the ratio of ingredients, and the corresponding ingredients are: 50% nanocellulose, 59% tert-butanol.

(7) The difference from (1) lies in the ratio of ingredients, and the corresponding ingredients are: 60% nanocellulose, 40% tert-butanol.

The difference between (8) and (1) is that the proportion of ingredients is different, and the corresponding ingredients are: 60% nanocellulose, 50% tert-butanol.

The difference between (9) and (1) is that the proportion of ingredients is different, and the corresponding ingredients are: 60% nanocellulose, 59% tert-butanol.

The key technology of the present invention is to investigate the effect of different ingredient ratios on the hydrophobic modification and anti-moisture filtration of nanocellulose air purification membranes, and to construct air purification membranes with different densities and hydrophobic properties by changing the ingredient ratios; tert-butanol ingredients The increase of the ratio effectively reduces the density of the air purification membrane, further optimizes the pore structure of the air purification membrane, increases the specific surface area, and improves the basic filtration effect of particulate matter in different air environments; the main influence of the different ratio of nanocellulose ingredients The hydrophobic performance of the air purification membrane is improved, and the water contact angle of the air purification membrane is optimized to improve its anti-moisture interference ability, which effectively reduces the problem of increasing the filtration resistance caused by the condensation of humid air, and can realize the nanocellulose air purification membrane in high humidity air. under the effect of stable filtering.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose thereof is to enable those of ordinary skill in the art to understand the content of the present invention and implement them accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the essence of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. the preparation method of super-hydrophobic nano-cellulose anti-moisture air purification membrane, is characterized in that: comprise the steps: 1) Prepare 40-60 parts by weight of nanocellulose, 0.1-1 part of methyltrimethoxysilane, 40-60 parts of tert-butanol, 2-4 parts of purified water, and mix the nanocellulose and tert-butanol evenly , and placed under ultrasonic conditions to homogenize; 2) Adjust pH=4 with pure water, add methyltrimethoxysilane, and stir to prepare a silane hydrolyzed solution; 3) Mix the material obtained in step 2) with the material obtained in step 1), carry out a modification reaction under stirring conditions, use a custom mold to shape after the modification reaction, freeze-dry, and anneal at high temperature to obtain superhydrophobic nanofibers Anti-moisture air purification membrane. 2. the preparation method of super-hydrophobic nanocellulose anti-moisture air purification film according to claim 1, is characterized in that: in step 1), according to 50 parts of nanocellulose, 0.5 part of methyltrimethoxysilane, tert-butanol The weight ratio of 50 parts and 3 parts of purified water. 3. the preparation method of super-hydrophobic nanocellulose anti-moisture air purification membrane according to claim 1, is characterized in that: the stirring described in step 1) is uniform, is to adopt magnetic stirring 30min. 4. the preparation method of super-hydrophobic nanocellulose anti-moisture air purification membrane according to claim 1, is characterized in that: the ultrasonic condition described in step 1), its power 100W, time 10min. 5. the preparation method of super-hydrophobic nanocellulose anti-moisture air purification membrane according to claim 1, is characterized in that: the described stirring in step 2) is to adopt magnetic stirring for 10min. 6. the preparation method of super-hydrophobic nano-cellulose anti-moisture air purification membrane according to claim 1, is characterized in that: described in step 3) carry out modification reaction under the condition of stirring, is to carry out modification under magnetic stirring. Sex 2h. 7. the preparation method of super-hydrophobic nano-cellulose anti-moisture air purification film according to claim 1, is characterized in that: the described use custom-made mould shaping of step 3), wherein the size of mould R=6cm, height is 2cm . 8. The preparation method of the super-hydrophobic nanocellulose anti-moisture air purification membrane according to claim 1, characterized in that: the freeze-drying described in step 3) is first placed in a refrigerator, pre-frozen at -20°C for 6h, Then it was placed at -56°C for drying for 48h; the high temperature annealing was performed at 80°C for 2h. 9 . The super-hydrophobic nanocellulose anti-moisture air purification film is characterized in that: obtained by the preparation method of the super-hydrophobic nanocellulose anti-moisture air purification film according to any one of claims 1-8.

Images